HR: 1340h
AN: MR33A-0154    [Abstracts]
TI: P- and S-wave velocity measurements on saturated siliceous conglomerates: determination of frame moduli
AU: * He, T
EM: tieweihe@phys.ualberta.ca
AF: Univ. of Alberta, Inst. for Geophysical Research, Dept. of Physics, Edmonton, AB T6G 2J1 Canada
AU: Schmitt, D R
EM: schmitt@phys.ualberta.ca
AF: Univ. of Alberta, Inst. for Geophysical Research, Dept. of Physics, Edmonton, AB T6G 2J1 Canada
AB: Reservoir conditions, such as the pore pressure and the fluid saturation levels, will change during the production of fluids from the earth. These changes will also influence the seismic wave properties of the rock. In order to better understand its seismic response, compressional and shear wave velocities were measured on a series of low porosity (less than 10%) conglomerates under different confining and pore pressures under both dry and water saturated conditions. P- and S-wave velocities were simultaneously measured using standard pulse transmission methods. In all cases, the velocities increased dramatically with effective confining pressures to 60 MPa. As expected, saturated P-wave velocities were always greater than those under `dry' (i.e. pore space under vacuum) conditions. Conventional assumptions leading from Gassmann's relations suggest that the S-wave velocity would drop; however, in this study the S-wave velocity increased after saturation. The contradiction of the observed data with the theory has been attributed to a number of mechanisms, such as viscous coupling, the reduction in free surface energy, and frequency dispersion due to local flow of the fluid in the microcracks. The pore geometry, the microcracks and the clay content are among the most important factors influencing the seismic properties of these rocks. These geological factors are characterized though thin section, Scanning Electron Microscope (SEM), and Hg-porosimetry. The stress sensitive intra- and inter-grain cracks observed through these images play an important role in the velocity pressure relationship. The variation of the Vp/Vs and Poisson's ratios as functions of the effective pressure are also shown.
UR: http://www-geo.phys.ualberta.ca
DE: 0935 Seismic methods (3025, 7294)
DE: 0994 Instruments and techniques
DE: 5102 Acoustic properties
DE: 5114 Permeability and porosity
DE: 5194 Instruments and techniques
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005